<%@ page import="java.util.HashSet" %><%--
  Created by IntelliJ IDEA.
  User: Admin
  Date: 2017/10/12
  Time: 11:49
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<%

    HashSet sessions=(HashSet)application.getAttribute("sessions");

    out.print(sessions.size());

%>
</body>
</html>
